There is no way to force 1 player, you can only warn them in your description.
Make a good level
Make a really good level
You just make a Mortal Kombat level that's a fighter
Make a good level
Use options to make it a favorite
Just make a good level.
You just go to create mode and make anything
There is a glitch to do this. Just consult the level '3D level glitch' for more info
All you do is go to the level edit and change it to versus i think that's how it is.
Complete story mode and use the stuff from story mode to create your level.
Use the corner editer. Use the grids to make stairs.Make sure to listen to the tutorials. Have a friend play your level before you publish it.
You can't give an answer really but I'll try. Littlebigplanet is basically the perfect game. Someone made a platformer but what if you don't like platformers? play a shooting level. Someone made a puzzle level but you can't do puzzles? play a racing level. What I'm trying to say is that there is something for everyone on littlebigplanet and if there isn't anything for you there yet you can easily make your perfect level yourself. If you don't like it still because of the effort you might have to put in, you can wait for the second littlebigplanet which isn't that far away now.